1. Field of the Invention
The present invention relates to a solder ball attaching system and method for micro ball grid array packages, and more particularly, to a solder ball attaching system and method, which is capable of performing a solder ball attaching operation inside a single equipment successively.
2. Description of the Related Art
Recently, semiconductor products, which play a pivotal role for development of industry extending into electric, electronic, machine and aerospace industries, have been developed steadily in the technology.
To manufacture such semiconductor products, it must go through a semiconductor chip manufacturing process for manufacturing a semiconductor chip, a semiconductor chip packaging process for protecting the friable semiconductor chip and signal input-output between the semiconductor chip and an external equipment and a testing process.
Actually, the development of the semiconductor chip manufacturing technology and the improvement of performance of equipments of precision process for manufacturing the semiconductor chip have made the manufacture of a highly integrated semiconductor chip possible. Moreover, in the semiconductor chip package process, the development of the semiconductor packaging method and the improvement of efficiency of process equipment for manufacturing the semiconductor package have made the increase of efficiency of semiconductor products and the miniaturization of the semiconductor products.
Especially, a ball grid array package, which is mainly used for the highly integrated semiconductor products having lots of input/output terminals, has been disclosed. The ball grid array package is easier in treatment than a PGA(Pin Grid Array), in which signal input/output between the external device and the semiconductor chip is performed by I/O pins arranged in matrix type. Moreover, the ball grid array package, which is small in size, is what is called “chip scale package” that the whole size of the semiconductor product is about 120% of that of the semiconductor chip, and uses solder balls as input/output terminals in place of pins.
The ball grid array package, in state that the semiconductor chip is attached on a printed circuit board forming circuit pattern on both sides or on a non-circuit side of a flexible board having the other side forming the circuit pattern, connects a bonding pad of the circuit pattern and the semiconductor chip in various way, for example, a beam lead bonding, a wire bonding or others.
At this time, the circuit pattern is connected to a portion of a circuit pattern called as “solder ball pad” and performs electric signal input/output with the external device through the solder ball pad.
The semiconductor chip is wrapped with molding resin to protect it from external shock and force and a solder ball is attached on the solder ball pad by a solder ball attaching process for connection with the external device.
At this time, the solder ball attaching process is divided into a solder ball seating step that the solder ball is coated with a water-soluble flux and the solder ball is temporarily seated on the flux, a reflow step that the solder ball is melted and attached on the solder ball pad in a furnace of high temperature and a cleaning step for removing water-soluble d-solvent.
The solder ball seating step, the reflow step and the cleaning step are performed by a solder ball attaching equipment group. The solder ball attaching group includes a solder ball seating equipment for the solder ball seating step, a reflow equipment, a cleaning equipment and a loader equipment for storing the cleaned ball grid array package. The equipments are arranged in series and independently operated to perform their own step.
However, each of the unit equipments included in the typical solder ball attaching group are located closely with the related equipments, but as there is a long distance between the unit equipments, the area where the solder ball attaching equipment group occupies is very large.
Moreover, the solder ball seating equipment, the reflow equipment, the cleaning equipment and the loader equipment included in the solder ball attaching equipment group perform only their own process but not perform connection between the previous step and the next step. Therefore, the connection between the steps depends on an operator.
Furthermore, as the unit equipments of the solder ball attaching equipment group are arranged long and the operator must perform the connection between the steps, the operator's line of movement becomes long, thereby fatigue to the operator is accumulated, the period of time required to attach the solder ball on the ball grid array package becomes long, and the steps are not performed consecutively.
Additionally, even though the solder ball seating equipment is out of order and thereby the insertion of the ball grid array package into the reflow equipment and the cleaning equipment is delayed, as there is no connection between the steps, heating of the reflow equipment and cleaning solution feeding of the cleaning equipment are continued, thereby the equipments are easily deteriorated.
Moreover, additional loader equipment is required for storing the ball grid array package finishing the solder ball attachment. After starting the solder ball attaching process, as the operator must directly transfer all unloaded containers to the loader equipment, the automatization of the solder ball attaching process is difficult.
Furthermore, to transfer the ball grid array package from one step to another step, the ball grid array package must be discharged out from the unit equipment and inserted into the next equipment. If the ball grid array package is discharged out from the unit equipment and inserted into the next equipment, there may cause a bad process, for example, the solder ball to be attached drops down from the solder ball pad. Even though such problem is continued, investigation of the factors leading to the bad process is very difficult.
Additionally, as the unit equipments of the solder ball attaching equipment group perform independently their own step, it is difficult to control the whole solder ball attaching equipment group and thereby lots of time is required for the process and the bad process occurs frequently.